rancher2-deployment: DRY_RUN must not connect Rancher

[bemeyert]

With the commits 3cc4667c4aa8e93261a96f3262931fe4c8825ed and 4c351d4 DRY_RUN became more or less useless. The new code contacts a Rancher-cluster even if DRY_RUN is set. DRY_RUN is also for local testing and development. This would then only work if there is a working internet connection and Rancher credentials are setup.

To give DRY_RUN it's intended purpose back the connection to Rancher should not be done when DRY_RUN is set.